Normal Hair Cycle

Hair loss can result from many factors. Some of these include thyroid disease, high fever, diet, childbirth, and certain medications. The most common form of scalp hair loss is termed androgenetic alopecia (male and female pattern hair loss), and is not caused by poor circulation, clogged hair folicles, frequent shampooing, or the use of hats or helmets.

Male pattern hair loss is determined by a combination or heredity and male hormones called androgens which include testosterone and dihydrotestosterone (DHT). The tendency for male and female pattern hair loss is genetically inherited from either side of the family and begins to develop after puberty. Hair on the scalp that is genetically affected by DHT (generally the front and top of the scalp), starts to shrink until it is lost. Whereas hair at the back and sides of the scalp is permanent because it is not affected by DHT.

Normal hair loss cycle

ANAGEN The mature growth phase last 2-6 years		CATAGEN The hair follicle shrinks at the end of growing phase. This is the resting phase.		TELOGEN The hair follicle shrinks further and the hair shafts loosen within the follicular sheaths.

Norwood Hamilton scale

Hair Cycle Affected by DHT
The Anagen stage and regrowth of the hair becomes shorter and the growing hair becomes progressively more miniture in length and diameter until it dissapears. The follicle (or root) however remains viable and in some cases can be stimulated with medical treatments to regrow some hair. If successfull the medical treatment must continue or the new hair will regress again.